This project is designed to determine the anatomical basis of epileptogenesis in cerebral neocortex. Studies are being carried out in chronically implanted cats to test a hypothesis which says that interruption of cortico-cortical fibers between adjacent segments of cortex will raise seizure threshold as opposed to undercutting cortex which lowers thresholds over time. Anatomical studies using silver degeneration methods and electronmicroscopy are being performed to determine the origin, extent, and termination of the fiber systems involved. Seizure thresholds are being tested using electrical stimulation 1-3 times per week for up to 5 months.